The field of the invention relates generally to filtration systems for use in removing particulate matter from a stream of gas, and more particularly, to a filtration method and system that includes a conductive filter media.
Fabric filtration is a common technique for use in separating particulate matter from an air stream. Fabric filtration is often accomplished in a device known as a baghouse. A typical “reverse air” baghouse has a housing with an inlet chamber and an outlet chamber. The two chambers are separated by sheet metal, commonly referred to as a tubesheet. The tubesheet is typically located in the lower area of this type of baghouse. The tubesheet has a number of openings around which mounting thimbles are welded.
Filter bags are supported in the baghouse. The filter bags are attached at their lower end portions to respective mounting thimbles. The filter bags extend upwardly in the outlet chamber and are attached at an upper end portion to support structure. The filter bags are generally connected to attachments or tensioning devices at their upper end portions.
Particulate-laden gas is directed into the inlet chamber. The gas flows through the opening in the tubesheet, thimbles and filters into the outlet chamber. Particulates are separated from the gas stream at internal surfaces of the filter bags. The filtered gas is exhausted from the outlet chamber or directed for other uses. The filter bags are often made from a substantially non-conductive woven fiberglass filtration media material, or any other suitable filtration media such as knit or felt synthetic material.
The filter bags are periodically cleaned by reversing the flow of gas in the baghouse. In order to prevent the filer bag from collapsing inwardly on itself and restrict or pinch off cleaning gas flow, anti-collapse rings made from metal are attached to the filter bags. Ring covers attach the anti-collapse rings to the filter bags and are typically formed from woven fiberglass fabric that is folded and then sewn to form a pocket which contains the anti-collapse ring.
Often the inlet gas may contain flammable or ignitable material. This material may be ignited by sparks or discharge of built up static electricity. In some applications, static electrical charges tend to build up on isolated metal components of a filter bag. The static charges can cause process dust to accumulate unevenly on the filter media, tending to agglomerate near the location of the anti-collapse rings. A static charge allowed to build up creates a potential of a spark discharge to other nearby metal components. In some process dust applications, such a discharge could ignite the process dust or ignitable material to causes a fire or explosion in the baghouse. For safety, it would be desirable to remove and/or prevent the built-up static charges to prevent spark discharges.